Tag: blindness

Human eye. (a) The structures of the eye and (b) the retinal layers in detail. (c) The chip carries a microphotodiode array with amplifiers and electrodes and is surgically placed subretinally in the location corresponding to the layer of degenerated photoreceptors. Courtesy Katarina Stingl et al.

In people with hereditary retinal diseases like retinitis pigmentosa, the eyes’ photoreceptors, or light sensors, degenerate slowly over time, eventually leading to blindness. While these people are unable to see, the rest of their visual pathway remains intact and functional. Researchers in Germany now have a way to work around this roadblock by introducing an implant to take the place of the broken photoreceptors and restore some level of communication directly with a patient’s visual pathway.

The researchers implanted a tiny electronic device under the retina of patients to take the place of their non-functioning photoreceptors. The implant is only about a third of an inch squared—the size of a Chiclet—and converts light into electrical signals. It is powered wirelessly via a battery pack attached behind the patient’s ear.

Our ability to see depends on two factors: light-sensitive rods and cones in the retina, and the nerves that transmit signals from these cells to the brain (along with the brain itself, of course). When the rods and cones die, which can occur as the eye ages or in the retina-damaging eye disease retinitis pigmentosa, the nerves can sometimes still function—if they have a new, working sensor for light. To replace the rods and cones, previous treatments have used electronic implants, which require surgery, or gene therapy, which relies on injections deep into the eye. But in a new technique, all it takes to restore vision—at least partially—is a much less invasive injection of the chemical AAQ.

With VizWiz, the blind can take a picture, ask a question, and get an answer back from a real person in seconds.

What’s the News: With the web as their eyes, the blind will able to read menus, identify canned foods, and tell whether that park has any free benches without having to walk over. That’s the vision of a team of computer scientists behind an iPhone app called VizWiz, which lets people take a photo of whatever’s perplexing them, record a question like “What denomination is this bill?” and send it off to real people online who’ll respond in a matter of seconds with “That’s a 20.”

What’s the News: Neuroscientists have found a preliminary answer to a question that has puzzled philosophers for centuries: If someone who has always been blind is one day able to see, can they recognize by sight objects they already know by touch? In a new study published online by Nature Neuroscience, patients who had been blind since birth underwent sight-restoring surgeries as children or adolescent. In the day or two following surgery, patients seemed unable to match what they felt with their hands with what they saw, the researchers found, but a week later, they could.

This results suggests that the brain doesn’t have the innate ability (or maybe has limited innate ability) to tie input from different senses to the same concept—but that it can learn, and pretty fast. Just how fast, the researchers wrote, suggests that the neuronal machinery needed to bring together visual and tactile information may already be there; it just has to be started up.

Embryonic stem cell treatments are edging closer to mainstream medicine. An experimental treatment just approved for clinical trials may provide hope to the 10 to 15 million elderly patients in the United States who suffer from a common form of macular degeneration, which causes gradual blindness.

The biotech company behind the treatment, Advanced Cell Technology, Inc., previously won FDA approval to try an embryonic stem cell treatment on patients with a rare, juvenile form of macular degeneration. The new FDA-approved trial will use similar techniques, but targets a much broader patient base.

“ACT is now the first company to receive FDA clearance for two hESC (human embryonic stem cell) trials, and is now a true translational leader in the field of regenerative medicine,” said chief executive Gary Rabin. “It marks a major step forward, not just within the stem cell sector, but, potentially for modern healthcare techniques.” [AFP]

Embryonic stem cell treatments are finally breaking out of the lab and arriving in the clinic. In October, the first federally approved trial of a treatment derived from these controversial cells got underway in patients with spinal cord injuries. Now, the FDA has approved a second trial, this one to test a treatment for a rare disease that causes serious vision loss or blindness.

The company behind the trial, Advanced Cell Technology, will test the safety and efficacy of the treatment on 12 patients.

The trial will examine the safety of a therapy for Stargardt’s Macular Degeneration, an inherited juvenile eye disease affecting an estimated 1 in 10,000 young people in the US. As the disease progresses, a layer of the retina called the retinal pigment epithelium (RPE) degenerates, causing vision loss. It’s hoped the new therapy would also work for other types of macular degeneration, a widespread cause of blindness, particularly in the elderly. [Nature blog]

In an exciting pilot study, blind people equipped with microchips in their retinas were able to see again–at least dimly–and were able to make out shapes.

Ed Yong explains how the experiment helped a study participant named Miikka:

In people like Miikka with retinitis pigmentosa, the light-detecting cells of the retina break down with age. Eberhart Zrenner and a team of German scientists have designed a chip that does the same job as these defunct cells. Just a few millimetres across, it contains 1,500 light-detecting diodes that detect light and convert it into a current. The brighter the light that hits the chip, the stronger the current it puts out. The current is delivered directly to the bipolar cells, which would normally transmit the signals from the retina’s actual light detectors.

Find out more about how the technology works and get the full story on Miikka and his fellow experiment subjects at Not Exactly Rocket Science. And check out the videos of Miikka trying out his new eyes below.

The winners of the Lasker Awards, the top medical prizes given out in the United States, were announced today.

The Laskers, awarded by the Albert and Mary Lasker Foundation, are $250,000 awards generally regarded as good predictors of who will go on to win a Nobel Prize for medicine or chemistry. [ABC News]

The driver of obesity

Douglas Coleman and Jeffrey Friedman took home the prize in the first category, basic medical research. The pair discovered leptin, a hormone that governs body weight and appetite. Its discovery helped to explain parts of obesity that had never been understood.

When a person’s cornea is burned it’s not necessarily the splashed chemicals or hot liquids that causes blindness, but the eye’s recovery. Scar tissue, formed from cells in the white part of the eye, can cover the cornea in a cloudy haze. But researchers have found that cells drawn from another part of the body can correct the problem.

A paper published yesterday in the New England Journal of Medicine brings news of a regenerative stem cell treatment that has had striking success: It restored sight to 82 of 117 eyes with burnt corneas, and worked partially on 14 others. The treatment also seems to have a long-lasting impact; in one patient, the beneficial effect has lasted for ten years and counting.

The treatment offers hope to those who received little benefit from existing therapies–such as artificial cornea replacements, which can also be overpowered and clouded by white-colored cells, or stem cell or cornea transplants from cadavers, which patients can reject.

“[The patients] were incredibly happy. Some said it was a miracle,” said one of the study leaders, Graziella Pellegrini of the University of Modena’s Center for Regenerative Medicine in Italy. “It was not a miracle. It was simply a technique.” [AP]

The weird phenomenon of blindsight—in which people take in visual information about objects without actually “seeing” them—has long intrigued scientists, and with good reason. They’ve watched people navigate obstacle courses and identify colors while being technically blind. This week, in a study in Nature, neuroscientists point to a part of the brain called the lateral geniculate nucleus (LGN) as the neural key that might make blindsight possible.

They used macaques in which the primary visual cortex had been destroyed. The monkeys’ eye-focusing movements revealed that they were “seeing” images shown at the periphery of their visual field, but only if their LGN was intact [New Scientist].

The authors refer to the LGN as the “main relay” between the retina and main visual cortex.

Other work had shown that the LGN also has projections to a number of secondary visual areas, suggesting that it may serve as a major hub in the visual system. To test this suggestion, the authors injected the LGN with a chemical that activates the receptor for a major inhibitory signaling molecule…. When the chemical is present, nerve cells receive a signal telling them to stop signaling, so this this injection has the effect of shutting the LGN down entirely [Ars Technica].

When the scientists shut down the LGN, the primates in the study didn’t experience any blindsight, as it appears no information was reaching any of their brains’ visual centers.